When you firstly come to a supported website a new tab opens where you have to authorize the extension to use the Last.fm API. You need to do this only once, when the extension is firstly installed; it isn't needed on updates (which are automatic, of course).

The status of scrobbler is shown in the omnibox (the addres field) on the right by the icon. Optionally you can enable desktop notifications and Youtube specific statuses (as shown on the extension preview). Note that it may take a while to contact the server and the "Scrobbling" text won't be added until Last.fm server confirms the reqest.

If the song doesn't get recognized, you can manually correct the title by clicking on the scrobbler icon. (This works only when song is not recognized - question mark icon.)

To temporarily disable scrobbling, click the status icon in the omnibox.

How to get it?

Notice

Last.fm is providing links to these applications as a courtesy, and makes no representations regarding these applications or the information supplied on this page. Use at your own risk. Any questions, complaints or claims should be directed to the third-party developer.